Adenocarcinoma cells can hide

Urine cytology is a microscope test of shed cells, and one of its blind spots is that gland-forming cancers can look faint enough to blend into the background. (pubmed.ncbi.nlm.nih.gov) The main target of the Paris System for Reporting Urinary Cytology, first published in 2016, is high-grade urothelial carcinoma, the aggressive bladder cancer urine tests are built to catch. Reviews of the system say secondary tumors and unusual variants are less fully characterized in routine urine specimens. (pathologyoutlines.com) (pmc.ncbi.nlm.nih.gov) A 2025 Cytopathology study looked at 30 urine specimens with colorectal adenocarcinoma cells involving the urinary tract. The cases had initially been called high-grade urothelial carcinoma under the Paris System and were backed by CDX2 immunocytochemistry before morphologic re-review. (pubmed.ncbi.nlm.nih.gov) (read.qxmd.com) That matters because adenocarcinoma is a gland-forming cancer, not the usual urothelial cancer that dominates urine cytology practice. If the malignant cells are sparse or deceptively bland, the slide can look less alarming than the diagnosis turns out to be. (pathologyoutlines.com) (pubmed.ncbi.nlm.nih.gov) Pathologists often use immunocytochemistry, a stain-based test that tags proteins in cells, when morphology alone does not settle the tumor’s origin. CDX2 is one of those markers because it is a nuclear transcription factor associated with intestinal epithelium and is widely used to support colorectal origin. (pathologyoutlines.com) (nordiqc.org) CDX2 is helpful, but it is not exclusive to colon cancer. Reference sources note staining can also appear in some bladder and urachal glandular lesions, which is why pathologists use it as part of a panel rather than as a stand-alone answer. (pathologyoutlines.com) (modernpathology.org) In practice, spotting a few subtle abnormal cells can change the whole workup. A suspicious urine or body-fluid specimen can trigger targeted stains such as CDX2, prompt correlation with imaging or endoscopy, and shift the report away from a default urothelial-cancer frame. (pubmed.ncbi.nlm.nih.gov) (pathologyoutlines.com) The lesson from recent cytology teaching posts and the published literature is narrow but concrete: some adenocarcinoma cells do not announce themselves. On the right slide, the difference between “subtle” and “missed” is whether someone looks for an intestinal-type pattern and orders the right stain. (x.com) (pubmed.ncbi.nlm.nih.gov)